TSB's

Some owners of 2007-2014 Cadillac Escalades, Chevy Avalanche, Silverado, Suburban or Tahoe, GMC Sierra or Yukon or Hummer H2 vehicles may complain of an SES light and constant engine misfire. In some cases, they may also complain of an engine tick/knock noise.

During diagnosis, the technician may find no compression on the misfiring cylinder(s) with 100% leakage into the crankcase. (Yes, your initial guess is correct: the piston may be blown).

If a lighted borescope is available, inspect the top of the related piston(s) through the spark plug hole to check for piston damage. You may find melted or fractured piston dome area.

If piston damage is found, this may be the result of aftermarket ECM calibrations and/or aftermarket components. Inspect the aftermarket add-ons such as exhaust, ignition or intake system modifications. Determine if factory ECM calibration numbers and CVNs are present by following the latest version of 09-06-04-026.